The ear canal 10 (FIGS. 1 & 2) is generally narrow and tortuous and is approximately 26 millimeters (mm) long from the canal aperture 11 to the tympanic membrane 15 (eardrum). The lateral part is flexible and referred to as the cartilaginous canal 16 due to the underlying cartilaginous tissue beneath the skin 5. The medial part, proximal to the tympanic membrane, is rigid and referred to as the bony region 13 due to the underlying bone tissue. A characteristic first bend occurs roughly at the aperture 11 of the ear canal. A second characteristic bend 8 occurs roughly at the bony-cartilaginous junction and separates the cartilaginous region and the bony region. The dimensions and contours of the ear canal may vary significantly among individuals, but are generally narrow with little space for accommodating miniaturized components therewithin. The ear canal is generally sensitive to touch and pressure, particularly in the deeper region, which can readily experience discomfort, abrasion and trauma with pressure and rigid contact. Abrasion of the skin inside the ear canal due to hearing aid use is common and generally limits insertions to the lateral (outer) portions of the ear canal.
Placement of a hearing device inside the ear canal 10 (FIG. 1) is generally desirable for various electroacoustic advantages such as reduction of the acoustic occlusion effect, improved energy efficiency, reduced distortion, reduced receiver vibrations, and improved high frequency response. Placement inside the ear canal may also be desirable for cosmetic reasons, with many of the hearing impaired preferring to wear inconspicuous hearing devices. A canal hearing device can be inserted entirely or partially inside the ear canal. In the context of this application, a “canal hearing device” refers to any hearing device with sound delivery inside the ear canal, whether partially or fully inserted therein. This includes what is known in the hearing aid industry as Completely-In-the-Canal (CIC), In-The-Canal (ITC), invisible extended wear deep canal, as well as Receiver-In-the-Canal (RIC) devices.